I had luck with http://www.carsdirect.com/ last time I tried this - ended up purchasing in Dublin, vehicle transferred from Stockton, with low interest manufacturer finance on offer at the time.
Understand TCO, and the cost of finance. Cars are very much fungible commodities, the purchase of which, dealers use to initiate a transaction where their objective is to extract as much money from you as possible.
Know if you're getting a good deal, or when to walk. Canny neighbor did something similar. Got the (distant) cars direct price, then told local dealer,
I'm about to set off purchase this car for this price, this afternoon. If you can beat or match the price, the deal is yours. She didn't have to travel as far as she was anticipating.